A standard torsional vibration damper of the type used on the crankshaft of a combustion engine normally is comprised of a relatively light and a relatively heavy mass. The light mass is rigidly fixed to the shaft whose oscillations are to be damped and is connected via an elastomeric body with the relatively heavy mass.
Such a device has the function of damping angular oscillations. The heavy mass has a resonant frequency with respect to the light mass which is increased by the mass of the shaft. This resonant frequency is a function of the mass of the heavy mass and the spring constant of the elastomeric body. Normally the resonant frequency is set so that it is approximately equal to that of the shaft. Thus as the damping mass resonates it uses energy and thereby damps the vibrations in the shaft.
This system has the considerable disadvantage that its service life is normally relatively short. Since virtually all of the energy absorbed in the damping action is transformed into heat, the elastomeric body becomes relatively hot. Normally such elastomeric bodies are poor conductors of heat so that in a relatively short time they disintegrate due to the heat. This can be reduced by making the elastomer relatively stiff, which requires an even heavier mass connected to it to achieve the desired resonant frequency. The result is a bulky assembly which will still have a relatively reduced service life. As such a device is normally mounted directly on the engine crankshaft, replacing it is an extremely difficult chore.